Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheets that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass typically refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two sheets of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area. Safety glass also can be used to provide other beneficial effects, such as to attenuate acoustic noise, reduce UV and/or IR light transmission, and/or enhance the appearance and aesthetic appeal of window openings.
Laminated safety glass can also include a layer of a polymer such as polyethylene terephthalate (PET), which can be used to impart various optical qualities to the final laminated glass product. For example, a polyethylene terephthalate layer can be used to support a printed image or can be treated with agents that selectively absorb certain wavelengths of light, thereby altering the visual appearance or final light transmission characteristics of the finished glass panel.
In many architectural applications it is desirable to use safety glass that not only has the proper physical performance characteristics for the chosen application, but also has light transmission characteristic that are unique, decorative, and/or particularly suitable to the end use of the product. For example, it will often be desirable to limit visible light transmission through laminated safety glass in order to provide a degree of visual separation between two adjacent areas or to modify the visual appearance of a laminated glass panel so as to create a desirable appearance. It may be desirable, for example, to utilize a laminated glass panel featuring patterns, colors, or visual effects that are different or the same when viewed from either side of the panel and that can provide varying levels of light transmission.
There is significant commercial interest in the fabrication of glass laminates with encapsulated printed images having novel patterns, colors, and light transmission qualities for use in architectural and automotive applications. A current state-of-the-art glass laminate product consists of an interlayer composite disposed between two glass sheets, wherein the interlayer composite comprises three layers. In this construct, a layer of polyethylene terephthalate that is printed on one side with a pattern is disposed between two layers of poly(vinyl butyral). Such interlayer composites effectively can be utilized to achieve glass laminates having a single pattern of light transmission, and, with the use of at least one layer of colored poly(vinyl butyral), can appear different in color from one side of the laminate to the other.
Further improved compositions and methods are needed to enhance the characteristics of laminated glass panels, and specifically laminated glass panels comprising poly(vinyl butyral) layers and polyethylene terephthalate layers, so as to impart desirable optical patterns and light transmission and reflectance qualities on the finished glass panel.